Chemotaxis is the directed movement of cells in a chemical gradient. It plays a major role in a large number of important biological processes, including embryology; wound healing, and cancer metastasis. The main aim of this Program Project is to extend our quantitative studies of chemotaxis using the model system Dictyostelium discoideum. Specifically, we will investigate the chemotactic process by dividing it into three projects with distinct timescales: 1) Directional sensing: the first response (0-10 s) of a cell following the exposure to an external Chemoattractant gradient, 2) Polarity: the subsequent (10-45 s) reorganization of the cytoskeleton, leading to an asymmetric (polarized) cell, and 3) Motility: the eventual (> 45 s) process of cell movement. For all projects, we will use a combination of quantitative experiments, aided by the use of microfluidic devices, and modeling approaches to further our insights into the mechanisms of eukaryotic chemotaxis.